bio__4 - DNA replication General structure of a nucleotide...

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DNA replication General structure of a nucleotide - Phosphate + Pentose + Purine or Pyrimedine base - Ribose and deoxyribose differ at this position at Pentose (H, OH) = only difference between DNA & RNA -DNA: has H group at Pentose -RNA: has OH group purines A, G two rings Adenine, Guanine pyrimidine s C, T single rings Cytosine, Thymine(DNA) Uracil(RNA) Griffith ’s bacterial transformation: Mouse injections 1) Virulent S strain = death: S colonies isolated from tissue of dead mouse 2) Nonvirulent R strain = healthy: R colonies isolated from tissue 3) Heat-killed S strain = healthy: No colonies isolated from tissue 4) Nonvirulent R strain + heat-killed S strain = death: R and S colonies from tissue of dead mouse Avery, MacLeod, and McCarty - transforming principle is DNA
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The Hershey-Chase experiment: DNA is the genetic material (not a protein)
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experiment: DNA is the genetic material (not a protein) Chargaff's rules - G + C content can vary widely among DNA from different organisms - [A] = [T] in all DNAs/ [G] = [C] in all DNAs Nucleotide chains are linear. 1. The 5¢ phosphate of one nucleotide is connected to the 3¢ hydroxyl of another nucleotide. Therefore the strand has polarity. 2. The bond formed is a phosphodiester bond or linkage. 3. The nucleotide chain therefore has a sugar phosphate backbone from which the nitrogenous bases hang. The exocyclic groups of the rings are potential hydrogen bond participants to make antiparallel DNA strands. The DNA is a double helix. - The nitrogenous bases of the two nucleotide chains face inwards with the sugar phosphate backbone on the outside of the molecule. - The paired bases are composed of one purine and one pyrimidine, always having G with C and A with T. The chains are said to be complementary due to this specific pairing of the bases. - The double helix is held together by hydrogen bonds that form between the complementary bases. - The two chains of the double helix are anti-parallel. Each chain has a different polarity (5¢ to 3¢ and 3¢ to 5¢).
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The double helix is complementary and anti-parallel. Separation of template strands forms a replication fork. - The replication fork moves as DNA synthesis proceeds. - Leading strand synthesis proceeds into the fork in a continuous fashion. - Lagging strand synthesis proceeds away from the fork in a discontinuous fashion. Enzymes responsible for replication - Helicase à unwinds double helix separates strands. - Binding proteins à stabilize each strand. - Primase à adds short RNA primer to template strand. - DNA polymerase à binds nucleotides to form new strands. - Ligase à joins Okazaki fragments and seals nicks in sugar phosphate backbone.
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Mitosis and Meiosis Three Steps to Cell Division (The Cell Cycle) - Interphase - Mitosis - Cytokinesis Cell Cycle 1. G1 (gap 1 or growth) - growth of the cell 2. S Phase (synthesis stage) - growth and replication of DNA 3. G2 (second gap)- growth & final preparations for cell division 4. M Phase - mitosis, actual separation of the replicated chromosomes and division of cellular components into two cells.
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